A little experiment in social giving and taking held this past August might provide some clues to the promotion and uptake of mobile money, and is well worth studying.

Jonathan Stark had a Starbucks card, and it's replicated on his iPhone. But he wanted to carry it on another phone. Which didn't have a Starbucks card So he took a screenshot of the app, and displayed that picture at the counter. The barcode still scanned, and he could get coffee from his card no matter what phone he was using.

But would it work if someone else had the picture?

So the picture was posted online, tens of thousands of people around the world not only paid for coffee, but reloaded the card and passed on the value to others - it only stopped when someone publicly declared they were skimming value off the card's account and putting over $600 on their own Starbucks card - at which point the Seattle based company decided to void the account (but not before publicly supporting it and getting a shed load of goodwill and PR).

So what lesions can be learned from this virtually enhanced store card?

I can spot a few clear takeaways. The first is that a lot of people are happy to try something if it doesn't have any cost to them to try it. And in the majority of people there is an intrinsic honesty, they'll play fair.

It's also about reduced friction. For all the discussion over magstripe readers, NFC chips, wave and pay... what's easier than a single JPG picture making the transaction? Reduce the complexity for the user and you're on to a winner. The "slippiest" mobile solution is going to be the winner.

And of course, all that can be destroyed by one bad egg, so how do you balance ease of use with the security needed?

These questions are all basic ones, but any system needs to not only be able to answer them, but keep them updated throughout the product cycle. The Market will happily experiment with new ideas, especially if nothing critical is riding on it. Capture them at that point, use their experiences, and build a better product. Be quick, be innovative, iterate, and don't be too afraid of failure.

And I'll have a short cappucino with caramel!